Page 11 - Black Range Naturalist Vol 3 No 3 July 2020

The only serious field study of southwestern porcupines was carried out by Dr. Walter P. Taylor in the early 1930s.3 Taylor did his studies on the Fort Valley Experimental Forest northwest of Flagstaff, Arizona. His report is too long to summarize here, but I think it is safe to conclude that porcupines were common. Concurrent with Taylor’s research were ongoing efforts to control porcupine numbers. We have no estimate of how many porcupines were killed in the forested areas of northern Arizona during the first half of the 20th century. However, if control efforts started in or before the 1930s and were still going strong when we encountered large numbers in the 1950s, we might conclude that they weren’t all that effective. The next significant summary of information on porcupines was published in 1989 by Uldis Roze of Queen’s College.4 An updated distribution map, dated 1982 and compiled by W. E. Dodge, expands the range of the porcupine southward into northern Mexico. Finally, a 1999 paper by Rurik List, Gerardo Ceballos and Jesús Pacheco5 documents records of porcupines as far south as Ceballos, Durango, Mexico (26°31'N, 104003'W) and includes Pleistocene occurrence as far south as Arroyo Cedazo in Aguas Calientes (21°52'N. 102°17'W). This series of maps might be construed as documenting an expanding porcupine range, but this most certainly is not the case. They represent increased awareness of the species and more accurate documentation of existing populations. In fact, List et al.postulate that porcupines were more abundant at the southern extent of their range during the Pleistocene and that current scattered occurrences are Pleistocene relicts.
More recently, mountain lions and black bears have been implicated in reduction of porcupine numbers.6 7 Taylor, in his early study, also considered pumas as a significant factor in controlling porcupines. Without solid, on the ground studies, these papers provide only hypotheses. Additional sources of mortality might be owners of working dogs: ranchers with stock dogs, lion and bear hunters with packs, and game bird hunters. Valuable dogs with faces full of quills do not contribute to the popularity of porkies.
One aspect of porcupine decline in their southern ranges that hasn’t been considered is the effects of climate change. If the small clusters of porcupines at the south end of their range are truly Pleistocene relicts, then we might expect a continuing decline in porcupine numbers with warming and drying trends.
In retrospect, thinking about the high densities of porcupines we saw on the Mogollon Rim in 1956, I realized that the Southwest was at the tail end of one of the most severe droughts in recorded history. Were we, perhaps, seeing a concentration of porcupines in the wetter meadows, along with more severe usage of
tree bark as a result of drought-caused food shortage? We’ll never know.
Figure 2. Approximate 1935 distribution of porcupines. U. S. Biological Survey. Taylor, 1935.
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